I think I have legg-calve-perthes disease, how can I know for sure?

Imaging confirms. Should consult orthopedic physician for examination. Plain radiographs show various stages of bone changes in hip from avascular necrosis. Earliest changes of ischemia to femoral head are noted on MRI and bone scan.
X-ray or MRI . A thorough orthopaedic exam is necessary to make the correct diagnosis. It will typically occurs in the 4-8 age group. X-ray and an MRI will confirm the diagnosis and treatment should be by a pediatric orthopaedist.